1. Field of the Invention
This invention relates generally to a method and apparatus for electrically stimulating a heart, and, more particularly, to a method and apparatus for positioning a multi-electrode lead to stimulate and/or sense activity in the heart.
2. Description of the Related Art
Since the introduction of the first implantable pacemakers in the 1960s, there have been considerable advancements in both the field of electronics and medicine, such that there is presently a wide assortment of commercially available body-implantable electronic medical devices. The class of implantable medical devices now includes therapeutic and diagnostic devices, such as pacemakers, cardioverters, defibrillators, neural stimulators, and drug administering devices, among others. Today's state-of-the-art implantable medical devices are vastly more sophisticated and complex than early ones, capable of performing significantly more complex tasks. The therapeutic benefits of such devices have been well proven.
Modem electrical therapeutic and diagnostic devices for the heart require a reliable electrical connection between the device and a region of the heart. Typically, a medical electrical “lead” is used for the desired electrical connection. One type of commonly used implantable lead is a transvenous lead. Transvenous leads are positioned through the venous system to attach or electrically connect at their distal end to the heart. At their proximal end, they are typically connected to the electrical therapeutic and diagnostic device, which may be implanted. Such leads normally take the form of a long, generally straight, flexible, insulated conductor. Among the many advantages of transvenous leads is that they permit an electrical contact with the heart without physically exposing the heart itself, i.e., major thoracic surgery is not required.
The specific design of transvenous leads is varied, depending upon the region of the heart to which it is to be connected. For example, U.S. Pat. No. 6,070,104 discloses an implantable lead capable of stimulating and/or sensing multiple chambers of the heart. Multiple electrodes are located on the lead and spaced apart so that multiple chambers may be separately stimulated and/or sensed. The structure and size of patients' hearts varies considerably. Accordingly, the optimal locations for positioning the electrodes within a vein may vary substantially, depending on the anatomy of the patient The spacing of the electrodes, however, is relatively fixed. Thus, optimally positioning the electrode associated with the ventricle of the heart may produce less than optimal positioning of the electrode associated with the atrium, or vice versa.